1. Field of the Invention
This invention relates to a sealing ring assembly in which the stepped cut surfaces of a sealing ring body are prevented from sticking to each other, thereby making it possible for the sealing ring assembly to be used for an extended period of time while vibrating under conditions of high temperature and pressure.
2. Description of the Prior Art
As shown in FIG. 1, a sealing ring body 4 made of synthetic resin includes stepped cut surface portions 5 having opposing planar portions 9 in contact with each other. When the sealing ring body 4 is fitted into the ring groove of a self-lubricating compressor piston, a fluid path is formed as indicated by the arrows, as a result of which leakage of high-pressure fluid occurs. To solve this problem, a sealing ring assembly is constructed by combining the sealing ring body 4 with a gas sealing ring 6 made of synthetic resin and a ring 8 made of metal, as shown in FIGS. 2 and 3. This arrangement prevents the leakage of high-pressure fluid and enhances sealing effectiveness.
The gas sealing ring 6 has approximately the same height as the sealing ring body 4 and is in contact with an inner circumferential surface 10 of the sealing ring body 4. In general, the gas sealing ring 6 and sealing ring body 4 consist of PTFE (polytetrafluoroethylene). The metal ring 8 has approximately the same height as the ring 6 and is in contact with the inner circumferential surface of the gas sealing ring 6. The gas sealing ring 6 serves to close the inner circumferential side of gaps 12, 12' between the stepped cut surface portions 5 of the sealing ring body 4. As a result, a fluid which flows into the gap 12 cannot flow into the interior of a ring groove 2 (FIG. of a piston 1. In addition, a high-pressure fluid which flows into the ring groove 2 from between the upper surface of the sealing ring body 4 and upper surface of the ring groove 2 cannot flow into the gap 12' due to the presence of the gas sealing ring 6. Thus, the flow path shown by the arrows in FIG. 1 is not formed in the example of the sealing ring assembly of FIGS. 2 through 4, by virtue of which the assembly provides a highly effective seal. The metal ring 8 urges the sealing ring body 4 and gas sealing ring 6 in the direction of an inner circumferential surface 3 of a cylinder so that the outer circumferential surface of the sealing ring body 4 is brought into sliding contact with the inner circumferential surface 3 of the cylinder at a desired pressure. In FIG. 4, numeral 7 denotes the cut surface portion of the gas sealing ring 6, and numeral 7' denotes the cut surface portion of the metal ring 8.
When the above-described sealing ring assembly is installed in e.g. a self-lubricating compressor and is used for an extended period of time at high pressure while vibrating under a high temperature, the planar portions 9 of the stepped cut surface portions 5 stick together, and sticking also occurs between the inner circumferential surface 10 of sealing ring body 4 and the outer circumferential surface of the gas sealing ring 6, which are in sliding contact with each other, in the vicinity of the stepped cut surface portions. This sticking phenomenon, which occurs despite use of the PTFE material, inhibits the relative movement between the rings 4 and 6 and alters the tension of the sealing ring body 4. The sticking together of the planar portions 9 similarly alters the tension of the sealing ring body 4. This detracts from the sealing property of the sealing ring assembly, adversely affects the contact pressure with the inner circumferential surface of the cylinder, and impedes follow-up response.